Process for the spinning of the crystalline polymer of vinyl chloride



United States Patent New polymers of vinyl chloride were made known recently by the scientific and patent literature; they are differentiated from the already known vinyl chloride polymers in practice by a higher degree of isotaxy, a higher percent crystallinity and a consequent more elevated heat-resistance:

Solvay Belgian Patents 560,624 and 562,433; I. Furukawa, J. Polymer Science 26, 234236 (1957); G. Natta and P. Corradini, J. Polymer Science, 20, 251266 It is an object of the present invention to provide a new process for the production of textile fibres having excellent mechanical and thermal characteristics, from crystalline polyvinylchloride.

This process consists in dissolving the polymer in a solvent selected from tetrahydrofurane and cyclohexanone (the second one being preferable), at temperatures higher than 80 C., and in the spinning of the viscose in hot condition in coagulating baths constituted by aqueous solutions of alkali metal or ammonium sulfocyanides, zinc chloride or mixtures of two or more of them.

The use of those particular salt baths provides the advantage of a low cost, of a gradual and homogeneous coagulation of the thread and of an easy recovery of the solvent, as is more fully set forth hereinafter.

The preparation of the viscose is effected by dispersing the polymer in the shape of a powder in the solvent under quick stirring and finally by heating to a temperature of from 80 C. to 200 C. and preferably of from 100 C. to 130 C.

The concentration of the polymer in the viscose may be com-prised within much wider limits; if using cyclohexanone as a solvent, viscoses suited for the spinning in salt baths have been obtained with concentrations of from 5 to 40% The viscose so obtained are spun in hot condition, at temperatures of from 60 C. to 150 C. and preferably of from 80 C. to 105 C., in coagulating baths constituted by aqueous solutions preferably of ammonium sulfocyanide, sodium sulfocyanide, potassium sulfocyanide or mixtures thereof, or zinc chloride.

These salt baths permit an illimitated solubility of the solvent utilized for the viscose, and a gradual and homogeneous coagulation of the thread.

The concentration of the salt baths varies, for any given viscose, as a function of the salt employed, as will be indicated in the examples, at any rate, the suitable concentrations vary within very wide limits, always permitting a very good coagulation of the thread; depending on the salt employed they may vary from to 70% and preferably from to 60% of salt.

The maximum concentration of the solvent admissible in the coagulating baths is 22% The stretching takes place at temperatures not sensibly lower than 100 C. in a small basin about cm. long, containing water or inert substances boiling at temperatures higher than 100 C. such as for instance ethylene glycol. The stretching may also be carried out between metal plates or on rolls kept at a suitable temperature or using any conventional stretching method that permits a heating of the thread to be stretched, to tem- 3,327,037 Patented June 20, 1967 ICC peratures not lower than C. The stretching ratios vary from 1:4 to 1:11 and are preferably in the order of magnitude of 1:8.

The process here claimed permits to obtain fibres hav ing excellent mechanical properties.

The use of saline coagulation baths according to the present invention finally permits a very easy recovery of the organic solvent; the recovery may take place by means of distillation, or by means of extraction with a second solvent not miscible with the aqueous phase, for instance methylene chloride, as well as by employing the very vinyl chloride monomer as an extracting means.

The modalities of the process are illustrated in the following examples:

Example 1 The crystalline polyvinylchloride used for the production of textile fibers is obtained by polymerizing, during 4 hours at the temperature of -40 C., 600 g. of monomer in the presence of 0.6 g. of normal boron tributyl as a catalyst and of 49.2 ml. of oxygen. To 735 parts of cyclohexanone are added under stirring parts of crystalline polyvinyl chloride having an intrinsic viscosity of 1.46. (The viscosity is measured by means of an Ubbelohde viscosimeter by the ASTM-Dl243-58T method. The viscosimeter has a flowing time for pure cyclohexanone that is 56 seconds at 30 C.) To complete the dissolving of the polymer, the mixture is heated to 20 C. for about two hours. The viscous solution obtained is spun through a spinneret with 48 holes in a coagulating bath at 80 C. constituted by a 20% aqueous solution of ammonium sulfocyanide. The thread is collected at a speed of 15 metres/minute and is stretched in boiling water at the ratio 1:8. The characteristics of the thread obtained are as follows:

Titre den 1.55 Tenacity g./den 4.08 Elongation percent 49.2 Young modulus 55.0

The coagulating bath containing 16% of cyclohexanone is distilled and the fraction passing over at 96 C. is collected. The distillate forms two layers, which are separated; the aqueous phase (lower layer) is sent to the coagulating bath, whilst the organic phase (upper layer) is purified from water by mere cooling. In that way, pure cyclohexanone is obtained.

Example 2 80 parts of crystalline polyvinylchloride, having an intrinsic viscosity of 1.38, obtained by the process of Example l, are dissolved in 490 parts of cy-clohexanone following the already described procedure. The viscous solution is spun in a coagulating bath kept at the temperature of 80 C. and constituted by a 30% aqueous solution of ammonium sulfocyanide. The characteristics of the thread stretched at a ratio of 1:8, by the method described in Example 1, are as follows:

Titre den 1 Tenacity g./den 4.51 Elongation percent 26.2 Young modulus 55.0

chloride and cyclohexanone one takes away the vinyl chloride by distillation at room temperature.

Example 3 95 parts of crystalline polyvinylchloride as obtained by the process of Example 1, having intrinsic viscosity of 1.38, are dissolved in 920 parts of cyclohexanone by the method described. The viscose is spun using as a coagulating bath a 40% solution of Zinc chloride in water and is kept at the temperature of 70 C. The thread obtained as stretched with 1:8 ratio has the following characteristics:

Titre den 1.06 Tenacity g./den 5.08 Elongation percent 19.7 Young modulus 71.0

The recovery of the cyclohexanone from the coagulating bath takesplace by any one of the methods already described in Examples 1 and 2.

Example 4 120 parts of crystalline polyvinyl chloride as obtained by the method of Example 1, are dissolved in 1380 parts of tetrahydrofuran at 120 C. A viscose is obtained which is spun using as a coagulating bath a 20% solution of zinc chloride, kept at 50 C. The thread so obtained when stretched as in the preceding examples, has characteristics corresponding to that obtained according to Example 3.

Example 5 A viscose is prepared following the method described in Example 1, by dissolving 100 parts of crystalline polyvinylchloride having an intrinsic viscosity of 1.37, in 650 parts of cyclohexanone. The viscose is spun using as a coagulating bath a solution constituted by 12.5 parts of sodium sulfocyanide, 12.5 parts of ammonium sulfocyanide and 75 parts of water. The temperature of the bath is kept at 70 C. After stretching in a ratio of 1:8 one obtains a thread having the following characteristics:

Titre den 0.94 Tenacity g./den 5.11 Elongation percent 18.5 Young modulus 45.0

The recovery of the cyclohexanone from the coagulating bath is carried out by any one of the already cited methods.

We claim:

1. A process for the preparation of filaments of crystalline polyvinylchloride, characterized in that the crystalline polyvinylchloride is dissolved at a temperature higher than 80 C. in a solvent selected from the group consisting of tetrahydrofurane and cyclohexanone and in that the resulting viscous solution is spun in coagulating baths constituted by aqueous solutions selected from the group consisting of alkali metal and ammonium sulfocyanides, Zinc chloride and mixtures of two or more thereof.

2. A process according to claim 1, wherein the temperature of dissolving of the crystalline polyvinylchloride in the organic solvent ranges from 100 C. to 130 C.

3. A process according to claim 1, wherein the concentration of the crystalline polyvinyl chloride in solution in the organic solvent ranges from 5 to 40'.

4. A process according to claim '1, wherein the temperature of the spinning bath ranges from 50 C. to C.

5. A process according to claim 1 wherein the concentration of the inorganic salts in the coagulating bath ranges from 10 to 70%.

6. A process according to claim 1, wherein the filaments produced have a tenacity not less than 4 grams/ den., the viscose produced by dissolving the crystalline polyvinylchloride in the solvent consists of 5 to 25 percent by weight of polyvinylchloride and from to 75 percent of solvent, the aqueous solution constituting the coagulating bath consists of 15 to 60 percent of the salt in solution, and the spun and coagulated filamentary material is stretched to produce the filaments.

7. A process according to claim 6, wherein the stretching is carried out at temperatures ranging from C. to C., with ratios ranging from 1:8.

8. A process according to claim 6, wherein the viscose consists of from 86 to 91.7 percent of solvent and from 14 to 8.3 percent by weight of polyvinylchloride having an intrinsic viscosity of from 1.46 to 1.37, and wherein the bath consists of an aqueous solution of a salt selected from the group consisting of sodium and ammonium sulfocyanides and zinc chloride, said solution including from 20 to 40 percent of the salt, and the spun and coagulated filamentary material is stretched to produce the filaments.

9. A process according to claim 8, wherein the filaments produced have a tenacity greater than 4.5 grams/ den., the polyvinylchloride has an intrinsic viscosity of 1.38, the polyvinylchloride is dissolved in cyclohexanone, the viscose consists of about 14 percent by weight of polyvinylchloride and of about 86 percent by weight of cyclohexanone, the coagulating bath consists of an aqueous solution of a salt selected from the group consisting of sodium and ammonium sulfocyanides and includes from 25 to 30 percent by weight of the salt and is maintained at a temperature of from 50 C. to 80 C., and the spun and coagulated filamentary material is stretched to produce the filaments.

References Cited UNITED STATES PATENTS 2,984,593 5/1961 Isaksen et a1 260-30.4 X 3,011,859 12/1961 Knudsen 264203 3,097,053 7/1963 Kurioka 264182 3,183,201 5/1965 Shimeha et al. 3,236,825 2/1966 Gord 264--219 FOREIGN PATENTS 917,889 2/ 1963 Great Britain. 37-2114 5/1962 Japan.

ALEXANDER H. BRODMERKEL, Primary Examiner. ROBERT F. WHITE, Examiner.

F. S. WHISENHUNT, J. H. WOO, Assistant Examiners. 

1. A PROCESS FOR THE PREPARATION OF FILAMENTS OF CRYSTALLINE POLYVINYLCHLORIDE, CHARACTERIZED IN THAT THE CRYSTALLINE POLYVINYLCHLORIDE IS DISSOLVED AT A TEMPERATURE HIGHER THAN 80*C. IN A SOLVENT SELECTED FROM THE GROUP CONSISTING OF TETRAHYDROFURANE AND CYCLOHEXANONE AND IN THAT THE RESULTING VISCOUS SOLUTION IS SPUN IN COAGULATING BATHS CONSTITUTED BY AQUEOUS SOLUTIONS SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL AND AMMONIUM SULFOCYANIDES, ZINC CHLORIDE AND MIXTURES OF TWO OR MORE THEREOF. 